But the new study falls short because it relies only on microscopic analysis, with no additional CAT scans or chemical tests, he said.

"They merely looked at the tissues and said, Oh, they're straight and well organized it must be collagen," Unwin said.

In some cases, he said, the fibers do look like collagen.

"But what they didn't draw attention to is that there are other tissues in there that don't look like collagen and might be protofeathers."

And what about the many other dinosaurs that appear to have been feathered?

Feduccia, the study co-author, says these creatures are actually descendants of birds that lost their ability to fly.

"When they become flightless, they superficially resemble small dinosaurs," he said.

Minority View

Storrs Olson, the curator of birds at the Smithsonian Institution's National Museum of Natural History, has been a vocal critic of the theory that modern birds evolved from dinosaurs.

"The whole notion of feathered dinosaurs is a myth that has been created by ideologues bent on perpetuating the birds-are-dinosaurs theory in the face of all contrary evidence," he said.

National Geographic magazine and other media have heavily publicized stories about feathered dinosaurs. But contrarian views struggle to get heard, Feduccia said.

"One of the primary arguments used to deflect our view is that we are a fringe group," he said. "But if science operates by a majority view, we're in serious trouble.

"We are dealing here basically with a faith-based science where the contrarian view is silenced to a large extent by the popular press," he added.

The University of Leicester's Unwin said that science benefits from opposing views, "because it keeps the people who are arguing for a dinosaur origin for birds on their toes."

But, "to be brutally honest, the contrarian views on this issue haven't been particularly strong," he said. "I don't know if they have really helped shape our ideas about the origin of birds in any serious way.

"One way the [latest] paper may be significant, though, is that it suggests that the story of the origin of feathers may not be quite as simple as we would like to have it."